I think it’s not a hard claim to agree with – some instances of purely cognitive content can feel aesthetic too. People are comfortable with the idea of the elegance of math, even if most concurrently claim that they haven’t personally experienced it.
There is a YouTube channel (yes, I consume all my media from tech monopolies and their children products) which consistently makes me brush against this feeling, and I think, has a lot to add to this world. It’s 3Blue1Brown, a math educator who’s turned to YouTube as a full-time job now.
When working with Processing, one of the first things I did was make a fractal tree. It’s pretty without much trying, because there’s a visual symmetry that we’re naturally attuned to pick out.
Anyways I recently looked at this video and thought about fractals again. The below video is mathy, though it uses no vocabulary (technical or otherwise) that a high-school graduate wouldn’t have. And that’s one of the great successes of this channel – it recounts very deep mathematical insights that most STEM undergrads would learn in class (perhaps even, as bonus material) with so little pomp and yet comes out feeling as obvious as I’ve experienced in my best lectures.
Plus his videos do an amazing job of rendering geometric relationships to the viewer – there’s a lot of design thinking in how the animations come out.